text: The ratio of SPINA-GT and thyroid volume V (as determined e.g. by ultrasonography)
  i.e.
  or
  is referred to as specific thyroid capacity (SPINA-GTs). It is a measure for how much one millilitre of thyroid tissue can produce under conditions of maximum stimulation. Thereby, SPINA-GTs is an estimate for the endocrine quality of thyroid tissue.